One clinically recognized treatment for chronic atrial fibrillation includes ablating the tissue surrounding the pulmonary vein ostia at the site in the intrapericardial space where the veins enter into the atria. Cardiac surgeons have described entering the chest through multiple thoracotomy incisions, using an endoscope and endoscopic instruments to dissect a tract under the superior vena cava and the inferior vena cava, and threading an ablation probe around the four pulmonary veins. In some of these cases, a surgical robot has been used to assist in the procedure. The probe enters posterior to the superior vena cava, winds through the transverse sinus of the pericardium, loops around the four pulmonary veins, and exits the tract that was dissected posterior to the inferior vena cava. The tract formed posterior to the superior vena cava enters into the transverse sinus of the pericardium. The tract formed posterior to the inferior vena cava completes the path of the ablation probe around the pulmonary veins.
In another technique to perform robotic probe placement endoscopically, one endoscope is advanced through a thoracotomy incision, or other entry incision, into the intrapericardial space adjacent the superior vena cava, and an endoscopic tool is inserted into the right pleural cavity via another thoracotomy incision. This latter endoscopic tool in the right pleural cavity is used to dissect through the right medial pleura and the pericardium posterior to the superior vena cava while being viewed with the endoscope. It is desirable to perform an ablation procedure using one set of endoscopic equipment and one endoscopic cannula.
In addition, encirclement of all four pulmonary veins with an epicardial ablation probe is hampered by two folds (known as reflections) of pericardium. One pericardial reflection forms the end of the transverse pericardial sinus and extends between the superior vena cava and the right superior pulmonary vein. The other pericardial reflection extends between the inferior vena cava and the right inferior pulmonary vein. It is relatively easy to dissect through the latter pericardial reflection, using an endoscopic subxiphoid cannula and a pericardial entry instrument. With the endoscopic subxiphoid cannula placed behind the heart in the oblique pericardial sinus, the pericardial reflection between the inferior vena cava and the right inferior pulmonary vein may be grasped by a pericardial entry instrument under endoscopic visualization, and an opening created through the reflection.
With the pericardial reflection between the superior vena cava and the right superior pulmonary vein, access is more difficult because this reflection forms the end of the transverse pericardial sinus and there is no direct way for the endoscopic subxiphoid cannula to approach this pericardial reflection. Without direct access and good visualization of this pericardial reflection, dissection is hazardous because the superior vena cava, right superior pulmonary vein, and right main pulmonary artery are all in the vicinity of the reflection. Grasping and forming a hole in the wrong structure, for example, the superior vena cava, would be disastrous.